The Extraordinary Botanical Diversity of Inselbergs in Madagascar
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The extraordinary botanical diversity of inselbergs in Madagascar Marina N. Rabarimanarivo, Brigitte Ramandimbisoa, Nivo H. Rakotoarivelo, Peter B. Phillipson, Sylvie Andriambololonera, Martin W. Callmander & Stefan Porembski Abstract RABARIMANARIVO, M.N., B. RAMANDIMBISOA, N.H. RAKOTOARIVELO, P.B. PHILLIPSON, S. ANDRIAMBOLOLONERA, M.W. CALLMANDER & S. POREMBSKI (2019). The extraordinary botanical diversity of inselbergs in Madagascar. Candollea 74: 65 – 84. In English, English and French abstracts. DOI: http://dx.doi.org/10.15553/c2019v741a8 Inselbergs are isolated mountains, mainly granitic or gneissic rock outcrops rising abruptly above surrounding plains. Malagasy inselbergs are often dome-shaped and occur in varying degrees of isolation, but they sometimes form inselberg landscapes, which comprise dozens of individual outcrops. Despite being typical landscape features on Madagascar’s high plateau, little data are available on their detailed plant cover. Recent extensive fieldwork, which was conducted between 2010 and 2014, mainly on the central plateau, has resulted in a better knowledge about the floristic composition and habitats of Malagasy inselbergs. The most speciose vascular plant genera were Cynorkis Thouars (18), Cyperus L. (15) and Euphorbia L. (14). Malagasy inselbergs are centres of diversity for succulents (notably species of the genera Aloe L., Euphorbia and Kalanchoe Adans.), carnivorous plants (species of Drosera L. and Utricularia L.) and resurrection plants (notably species of Xerophyta Juss.). The most speciose habitat types were ephemeral flush vegetation and monocotyle- donous mats. The latter habitat supports a large number of succulents and resurrection plants. In total 724 taxa out of 338 genera and 107 families have been recorded. Moreover, the variability in floristic composition between different regions is remarkable. Detrimental human impacts include quarrying, grazing, fire and the collection of plants for ornamental purposes (species of Pachypodium Lindl. and Orchidaceae) and as medicine (species of Aloe, Drosera madagascariensis DC., Myrothamnus moschatus (Baill.) Baill.). For the first time, recommendations are made for the conservation of Malagasy inselbergs. Addresses of the authors: MNR, BR, NHR, SA: Missouri Botanical Garden, P.O. Box 3391, Antananarivo 101, Madagascar. E-mail : [email protected] PBP: Missouri Botanical Garden, 4344 Shaw Blvd., St. Louis, Missouri 63110, U.S.A. and Institut de Systématique, Évolution, et Biodiversité (ISYEB), Muséum National d’Histoire Naturelle/Centre National de la Recherche Scientifique/ Sorbonne Universités/École Pratique des Hautes Études, C.P. 39, 57 rue Cuvier, 75005 Paris, France. MWC: Conservatoire et Jardin botaniques de la Ville de Genève, ch. de l’Impératrice 1, C.P. 71, 1292 Chambésy, Switzerland. SP: University of Rostock, Institute of Biosciences, Department of Botany, Wismarsche Str. 8, D-18051 Rostock, Germany. Submitted on February 1, 2018. Accepted on February 22, 2019. First published online on March 28, 2019. ISSN : 0373-2967 – Online ISSN : 2235-3658 – Candollea 74(1) : 65 – 84 (2019) © CONSERVATOIRE ET JARDIN BOTANIQUES DE GENÈVE 2019.